In any fluid flow control valve, control of fluid flow through the valve is achieved by moving a valve sealing element between open and closed positions. Mechanically activated valves have a full range of flow control capability from simple on-off or shutoff valves to precision flow control. Mechanically activated valves, however, have a number of points of contact between moving parts, resulting in friction that causes wear and eventual breakdown. Greater flow control is generally achieved only at the cost of a more complicated mechanical interface with more points of friction and wear.
Various types of magnetically activated valves are known (See, for example, U.S. Pat. No. 5,509,439), including mechanical valves adapted for operation by means of a magnetic driver, and other types, such as solenoid valves wherein the solenoid core shaft is also the valve sealing element (See, for example, U.S. Pat. No. 5,575,309). These valves have a problem of mechanical bearing of a core shaft, with resultant friction and wear. Such valves generally only work as shutoff valves, with no possibility of more precise fluid flow control.
U.S. Pat. No. 5,527,295 discloses a gravitational, magnetic, floating ball valve for use in the medical field as a protective fluid cut-off valve for infusion devices. The valve includes a hollow ball containing a magnet, which is arranged inside a vertical tube disposed in registration with an outlet. A second magnet is also disposed in vertical registration with the magnet. The magnet-containing valve is magnetically attracted towards the second magnet as the level of liquid in the infusion device decreases, sealing the outlet once the level of liquid in the infusion device drops to a predefined level.